Amber-colored excreta: a source of arrestment pheromone in firebrats, Thermobia domestica.

Female, male, and juvenile firebrats, Thermobia domestica (Packard) (Thysanura: Lepismatidae), employ a pheromone that arrests conspecifics on contact. Paper shelters placed in a T. domestica colony accumulate fecal excreta (= frass) and other insect-derived debris. Such shelters elicit arrestment by conspecifics. However, the definitive source of the arrestment pheromone was not known. We tested the hypothesis that one or more debris components from a T. domestica shelter constitute the source of the arrestment pheromone. In dual-choice, still-air olfactometer experiments, scales, exuviae, antennae, caudal filaments, gregarine parasite cysts, and silk (each intact or macerated) retrieved from shelters and separated for experiments, as well as saliva, hemolymph, and fat body extracted from insects all failed to arrest female T. domestica. Similarly, paper that had been fed upon by insects did not elicit an arrestment response, eliminating insect-altered cellulose as the arrestant pheromone. In contrast, insect-exposed glass significantly arrested females. Moreover, females were significantly arrested by (i) loose, insect-derived debris brushed from shelters, (ii) a frass mixture manually separated from loose debris, and (iii) specific amber-type frass manually separated from the frass mixture. These results lead us to conclude that amber-type frass constitutes the source of at least part of the T. domestica arrestment pheromone. [ABSTRACT FROM AUTHOR]